Self-heating or cooling container

ABSTRACT

This invention relates to a self-heating or self-cooling container ( 1 ), which uses an exothermic or endothermic re-action to provide or remove heat from the contents of the container. The chemical reaction includes a fluid consistuent (either as a reagent or solvent), held in a reservoir ( 6 ), which is added to another reagent in the reaction chamber ( 5 ) to initiate the reaction. The container ( 1 ) according to the invention proposes a means ( 8, 91 ) to control the volume of this fluid constituent added to the reaction chamber ( 5 ) depending on the ambient temperature of the container.

The present invention relates to self-heating and self-coolingcontainers, which rely on an exothermic or endothermic chemical reactionrespectively, to effect heating or cooling of a product held therein. Inparticular the invention proposes an arrangement to control the degreeof heating or cooling produced by the chemical reaction in response tothe ambient temperature of the container.

When the ambient temperature is higher a self-heating can will berequired to produce less heat to raise the temperature of the product inthe can to a desired temperature. If the exothermic reaction is notcontrolled, the container may become uncomfortable or dangerous tohandle.

Conversely, when the ambient temperature is higher, a self-cooling canwill be required to produce a greater cooling effect. Thus, theendothermic reaction will be required to absorb more heat.

Various methods of controlling the heat produced by a self-heating packin response to the ambient temperature have been suggested in the priorart. For example, U.S. Pat. No. 5,984,953 describes the use of a“stiffenable gel” to alter the rate of an exothermic chemical reaction,in conjunction with a vaporisable solvent which adjusts the stiffness ofthe gel, depending upon the ambient temperature conditions in which the“heating pack” is used.

The present invention requires the chemical reaction to include at leastone fluid constituent, either as a reagent or solvent. A temperaturecontrol arrangement, which is driven by the ambient temperature of thecontainer, acts to control the volume of this fluid constituent added tothe reaction. The fluid constituent may include substances such as gels,provided they are sufficiently mobile and able to flow.

Accordingly, the present invention provides a self-heating orself-cooling container which uses an exothermic or endothermic chemicalreaction to effect heating or cooling, the container comprising a bodyfor holding a product, a reaction chamber, for holding a primary fuel, areservoir for holding a fluid constituent, and an activation means forcreating a fluid flow path from the reservoir into the reaction chamber,characterised in that, the container further comprises a temperaturecontrol means, which responds to the ambient temperature of thecontainer to control the volume of the fluid constituent entering thereaction chamber.

Preferably the self-heating or self-cooling container includes areservoir (for holding the fluid constituent), whose volume may bereduced by a user of the container. As the volume of the reservoir isreduced, the fluid constituent is forced into the reaction chamberinitiating the chemical reaction.

Preferably the container has at least two parts, which are adapted tomove relative to one another. A first part of the container is coupledto a wall of the reservoir and the volume reduction of the reservoir isachieved by movement of this first part of the container relative to theother (second) part. The movement may be achieved by a user simply bypressing on the first part of the container. However, preferably thefirst and second parts of the container are coupled by a co-operatingscrew thread arrangement. A user of the container simply rotates firstpart of the container relative to the other part, to cause axialmovement of a wall of the reservoir, resulting in a volume reductionthereof. Such an arrangement allows controlled addition of the fluidconstituent to the reaction chamber because the rate of volume change ofthe reservoir and hence the rate of addition on the fluid constituent,is controlled somewhat by the pitch of the screw thread.

Advantageously, the fluid connection between the reservoir and thereaction chamber is provided by a conduit having a normally closed valvetherein. The fluid constituent is normally prevented from entering thereaction chamber by the valve, particularly during storage or transportof the container. However, upon activation of the reaction by a user,the valve opens to allow the fluid constituent to enter the reactionchamber, thereby initiating the chemical reaction.

Advantageously, the fluid constituent in the reservoir is pressurisedupon activation of the container by a user and the increase in pressureopens the valve and thereby the conduit between the reservoir and thereaction chamber. Thereafter, the valve is preferably adapted to closeitself, once the pressure in the reservoir is relieved. Thus, aself-closing valve (well known to those skilled in the art) may beincorporated into the conduit for this purpose.

Alternatively, the conduit may be normally blocked by a membrane or a“break-out” (connected to the conduit by a weakened section) which hasto be pierced before the fluid constituent can enter the reactionchamber.

In a first embodiment, the temperature control means takes the form of a“stop”, whose position is determined by the ambient temperature, therebycontrolling the volume of fluid constituent that can be forced into thereaction chamber. The “stop” comprises a physical stop member, which isdesigned to resist further activation of the container. The position ofthe physical stop member is controlled by a temperature sensitivematerial. Advantageously, the temperature sensitive material changes itsvolume depending upon the ambient temperature of its surroundings. Thus,if the material is constrained within a tube of constant cross section,for example, the physical stop member may be supported by the materialand its axial position within the reservoir controlled. The temperaturesensitive material may be chosen such that it expands or contractssignificantly in response to a change in the ambient temperature of thesurroundings. Suitable materials include certain waxes or greases, whichexpand in response to increased temperature, or materials such asHydrogels, which expand in response to a decrease in temperature.Hydrogels are particularly preferred because their volume changeslinearly with temperature.

Taking the example of a self-heating can: At increased ambienttemperatures, the exothermic reaction is required to produce less heat.Therefore, the exothermic reaction needs to be stopped before all thereagents have been used up. According to the invention, this is achievedby preventing full volume reduction of the fluid reservoir, therebyhalting the addition of fluid reagent to the reaction chamber.Therefore, when the ambient temperature is higher, the stop arrangementneeds to be designed such that the physical stop member prevents furtheractuation of the can by the user.

Where a wax or grease, which expands in response to increasedtemperature, is chosen as the temperature sensitive material, thephysical stop member needs to be coupled to the moving wall of thereservoir in order to stop movement of the wall earlier than could beachieved at lower temperatures. If a Hydrogel, which expands in responseto decreased temperature, is chosen as the temperature sensitivematerial, the physical stop member needs to be coupled to the stationarypart of the reservoir, to allow the greatest degree of movement of themoving wall of the reservoir, when the temperature is lowest and theleast amount of movement when the temperature is higher.

The “stop” may take the form of a mechanical arrangement, which isdesigned to amplify the expansion of chosen materials (metal, forexample) caused by the change in ambient temperature. Preferably, the“stop” is made from a material which itself undergoes significantexpansion or contraction in response to the normal variation expected inthe ambient temperature (i.e. 0° -40° C.). Such materials will be wellknown to those skilled in the art. The “stop” must both expand/contractsignificantly and also act as an effective stop i.e. it must also beable to resist further activation of the can by the user.

In a second embodiment of the invention, the self-heating orself-cooling container also comprises an auxiliary reservoir, into whichany fluid constituent, not required in the reaction is directed. In thecase of a self-heating can, one or more conduits are provided to thisauxiliary reservoir. The or each auxiliary conduit may be blocked by aplug, which melts in response to an increase in the ambient temperature.Preferably a plurality of conduits are provided, each blocked by a plug,which melts at a different temperature. Suitable chemicals for the plugsare taken from the family of paraffin waxes, which have discrete meltingpoints. For example, Hexadecane [melting point 18° C.], Palmitate (e.gPropylpalmitate [melting point 20° C.]) and Myristate (e.g BenzylMyristate [melting point 21° C.]). Thus, as the ambient temperatureincreases one or more plugs melt, opening the associated auxiliaryconduit. On actuation of the container by a user, a proportion of thefluid constituent is forced into the reaction chamber but a proportionis also forced into the auxiliary reservoir, where it takes no part inthe chemical reaction.

In this embodiment, one or more conduits may be provided between thereservoir and the auxiliary reservoir with a valve located therein whichprogressively opens in response to an increase in the ambienttemperature of the container. However, preferably a plurality ofconduits is provided to the auxiliary reservoir, each blocked by a plug,which melts at a different, predetermined temperature. As the ambienttemperature increases, so does the number of plugs that melt, openingmore of the conduits to the auxiliary reservoir and thereby increasingthe volume of fluid directed away from the reaction chamber.

The advantage of this arrangement is the simplicity of construction. Theplugs are simply small slugs of material, which melt at a definedtemperature.

Preferably, the plug material and material used to define the auxiliaryconduits (into which the plugs are placed) have a high surface tensionwith respect to each other, so that the plugs “cling” to the conduit andcan only be removed by melting. A step may also be defined in the wallof the auxiliary conduit, to prevent the plug being forced out of itsassociated conduit by the pressure applied to the fluid constituent.Again, the conduits and plugs are designed such that the plug may onlybe removed from its associated conduit by melting.

Finally, the fluid constituent may be provided in the form of a gel andthe reservoir arrangement may be designed such that the fluidconstituent itself substantially blocks the one or more auxiliaryconduits. As the ambient temperature rises, the gel becomes more mobileand a greater proportion of the gel is forced through the auxiliaryconduits to the auxiliary reservoir, rather than to the reactionchamber. In this arrangement the diameter and length of the or eachauxiliary conduit is critical in determining the volume of fluidconstituent entering the auxiliary reservoir, compared to that enteringthe reaction chamber.

The present invention will now be described by way of example only withreference to the accompanying drawings in which:

FIG. 1 shows a side, section view of a self-heating can according to afirst embodiment of the invention. In this embodiment a “stop” (whoseposition is determined by the ambient temperature) is arranged to limitthe volume reduction of the reservoir and thereby control the volume offluid constituent driven into the reaction chamber.

FIG. 2 shows a side, section view of a self-heating can according to asecond embodiment of the invention. In this embodiment an auxiliaryreservoir is provided into which a volume of the fluid constituent isdiverted, depending upon the ambient temperature.

Referring to FIGS. 1 and 2, a self-heating container according to theinvention comprises a can 1 having a body 2, a base 3 and an insert 4.The insert 4 defines a reaction chamber 5 for a primary fuel and areservoir 6 for a fluid constituent. The reservoir 6 is adapted toaccommodate a reduction in volume on actuation of the can 1 by a user.

Referring to FIG. 1, the floor 61 of the reservoir 6 is designed to moveaxially upon actuation of the can 1 by a user, thereby reducing thevolume of the reservoir 6. The insert 4 is fixed relative to the body ofthe can 2 and the floor 61 of the reservoir is rigidly coupled to thebase 3. The floor 61 of the reservoir 6 and the insert 4 have aco-operating screw thread arrangement 45, 65 to effect axial movement ofthe floor 61 relative to the insert 4. The periphery 62 of the floor 61is fixed to the base 3. Adjacent to the periphery 62, a flexiblediaphragm 63 is provided, to accommodate the axial movement of the floor61, whilst the overall length of the can 1 remains fixed.

In use, the user of the can 1 twists the base 3 relative to the body 2,the floor screw thread 65 and the insert screw thread 45 interact todrive the floor 61 of the reservoir axially by the progression of thereservoir thread 65 along the insert thread 45. This axial movement isaccommodated by the flexible diaphragm 63, which unfolds as the floor 61moves. The movement of the floor 61, reduces the volume of the reservoir6 and forces the fluid constituent (not shown) held therein along a flowpath (not shown) from the reservoir to the reaction chamber through thereservoir thread 65 and insert thread 45.

A pressure-activated valve 7, which is normally closed, is provided inthe flow path between the reservoir and the reaction chamber 5. Thevalve prevents accidental actuation of the can. However, once the userrotates the base 3 of the can 1, the volume of the reservoir 6 reducesas described above, pressurising the fluid constituent held therein, anddriving it through the flow path. The valve 7 opens in response to theincreased pressure and allows the fluid constituent to enter thereaction chamber 5.

In a first embodiment of the invention (shown in FIG. 1) the temperaturecontrol means comprises a “stop” 8, which expands in response to thetemperature of the can 1. In “normal” conditions the stop 8 is designedto exhibit no or limited expansion and the co-operating screw threads45, 65 progress relative to one another until the volume of thereservoir 6 is reduced to substantially 0 (i.e. when the floor 61 of thereservoir contacts the opposite boundary 66 of the reservoir 6). In thiscondition, the total volume of fluid constituent held in the reservoir 6is transferred to the reaction chamber 5.

However, when the ambient temperature is higher, the “stop” expands andlimits the progression of the threads 45 and 65 relative to one another.This in turn halts the axial movement of the floor 61 and thereby thevolume reduction of the reservoir 6. Thus, in this condition, a certainvolume of fluid constituent is retained in the reservoir 6 and only theremainder is transferred to the reaction chamber 5. Thus, the reactionis halted once the “stop” acts to limit the rotation of the base 3relative to the body 2.

Preferably, the “stop” is provided by a wax or grease held in a pistoncylinder. As the ambient temperature of the surroundings rises, the waxor grease expands, driving the piston outwardly of the cylinder. Thepiston acts as a mechanical stop to prevent further movement of thefloor 61 of the reservoir.

In a second embodiment of the invention (as shown in FIG. 2), the can 1also includes an auxiliary reservoir 9. The auxiliary reservoir 9 isconnected to the fluid reservoir 6 by a plurality of bypass flow paths91. A meltable wax plug (not shown) is provided in each flow path 91.

In “normal” conditions, the volume reduction of the reservoir 6 occursas previously described. All the fluid constituent is directed to thereaction chamber, because the meltable plugs remain solid and block thebypass flow paths 91. As the ambient temperature increases, some or allof the plugs melt and the associated bypass flow paths 91 open,providing fluid communication with the auxiliary reservoir 9. In theseconditions, only a portion of the fluid constituent is transferred fromthe reservoir 6 to the reaction chamber 5. The remaining portion isdirected to the auxiliary reservoir 9, where it takes no part in thechemical reaction.

As shown in FIG. 2, the flow path or paths between the reservoir 6 andthe reaction chamber 5 are normally blocked by a “break-out” 7′ prior toactivation of the can by a user. It will be appreciated that the valve 7shown in FIG. 1 may be replaced by a similar “break-out” to those shownin FIG. 2 and vice versa.

In this second embodiment, the base of the can 3 is provided with a basescrew thread 35, which rotates with the base 3. A moveable divider 61′separates the reaction chamber 5 from the reservoir 6 and is providedwith a screw thread arrangement 65, arranged to co-operate with the basescrew thread 35. The divider 61′ is prevented from rotating with thebase 3 by location rods 10.

In use, a user of the can 1 rotates the base 3, thereby rotating thebase screw thread 35. The divider is prevented from rotating with thebase 3 by the location rods 10. As the divider 61 is unable to rotate,rotation of the base 3 causes axial movement of the divider 61. The basescrew thread 35 and location rods 10, break the frangible connection ofthe “break-outs” 7′, opening the fluid communication between thereservoir 6 and the reaction chamber 5. Furthermore, as the divider 61moves axially, the volume of the reservoir 5 is reduced, driving thefluid constituent out of the reservoir 5. In “normal” design conditions,all the fluid constituent is transferred to the reaction chamber 5. Asthe ambient temperature rises above the “normal” design conditions, theplugs in the auxiliary flow paths 91 progressively melt and a proportionof the fluid constituent is bypassed to the auxiliary reservoir 9 andtakes no part in the chemical reaction. In this way, the chemicalreaction produces less heat, which prevents overheating of the productin the can 1.

The can 1, shown in FIG. 2 also has an arrangement of plates 15, 16,which are designed to accommodate restricted rotational movement. Theplates 15, 16 are used during the insertion of the plugs and also duringtransport of the can, when it may encounter temperature condition thatare different to those in which the can will be used.

Preferable the plugs are formed by filling the auxiliary flow paths 91with molten material, which is then allowed to set within the flow paths91. One of the plates 15, 16 is rotated to block one end of theauxiliary flow paths 91 and the molten material is then injected intothe other, open end of the flow path 91. When full, the other plate 15,16 is rotated to cover the other end of the auxiliary flow paths 91.Thus, if the can 1 is subjected to higher temperatures during transport,the plugs may melt but will be constrained within the flow paths 91 andwill re-set if the temperature reduces. Upon first activation of the canby a user, the initial rotation of the base 3 will move the plates 15,16 away from the auxiliary flow paths 91 and, depending on the ambienttemperature of the container, one or more of the plugs will have meltedand be forced into the auxiliary reservoir by the fluid constituent.

It will be apparent that certain of the features of the can shown inFIG. 2 may be applied to the can shown in FIG. 1 and vice versa.Furthermore, many other methods of sealing the fluid connection betweenthe reaction chamber and the reservoir will be apparent to those skilledin the art. For example, it is not beyond the scope of the invention toprovide a flexible reservoir for the fluid constituent (such as aflexible pouch), which is pierced upon first actuation of the can by theuser, to allow the fluid constituent access to the primary fuel in thereaction chamber.

Suitable exothermic and endothermic chemical reactions will also beapparent to those skilled in the art. One of the reagents may be a fluidor alternatively, the reagents may be provided in an inert solid formand the fluid constituent may take the form of a solvent, whichinitiates the chemical reaction by holding one or more of the reagentsin solution.

1. A self-heating or self-cooling container which uses an exothermic orendothermic chemical reaction to effect heating or cooling, thecontainer comprising a body for holding a product, a reaction chamberfor holding a primary fuel, a reservoir for holding a fluid constituent,an activation means for creating a fluid flow path from the reservoirinto the reaction chamber, and a temperature control means whichresponds to the ambient temperature of the container to control thevolume of the fluid constituent entering the reaction chamber wherein(i) the reservoir is adapted to accommodate a reduction in volume, thevolume reduction pressurizing the fluid constituent and thereby creatingthe fluid flow path into the reaction chamber, and (ii) the temperaturecontrol means comprises a stop, whose position automatically adjusts inresponse to the ambient temperature of the container, the stop arrangedto prevent further volume reduction of the reservoir and thereby toprevent further addition of the fluid constituent to the reactionchamber.
 2. A self-heating or self-cooling container according to claim1, wherein the reservoir comprises two portions, a housing portion and aplunger portion and the plunger portion is adapted to move within thehousing portion to produce the volume reduction of the reservoir.
 3. Aself-heating or self-cooling container according to claim 2, wherein theplunger portion is provided with a screw thread arrangement whichco-operates with a complimentary screw thread arrangement on the housingportion to effect movement of the plunger portion within the housingportion.
 4. A self-heating or self-cooling container according to claim2, wherein the plunger portion is anchored to the container and movementof the plunger portion is accommodated by a flexible diaphragm.
 5. Aself-heating or self cooling container according to claim 1, having afluid flow path between the reservoir and the reaction chamber, whereina valve is provided in the fluid flow path and the valve is adapted toopen in response to increased pressure within the reservoir.
 6. Aself-heating container according to claim 1, wherein the temperaturecontrol means comprises a material, which expands significantly inresponse to an increase in the ambient temperature of the container. 7.A self-heating container according to claim 6, wherein the material is awax or oil.
 8. A self-heating or self-cooling container according toclaim 1, wherein the temperature control means comprises a mechanicalarrangement, which expands significantly in response to an increase inthe ambient temperature of the surroundings.
 9. A self-heating containerwhich uses an exothermic chemical reaction to effect heating, thecontainer comprising: a body for holding a product, a reaction chamberfor holding a primary fuel, a reservoir for holding a fluid constituent,an activation means for creating a fluid flow path from the reservoirinto the reaction chamber; a temperature control means which responds tothe ambient temperature of the container to control the volume of thefluid constituent entering the reaction chamber; and an auxiliaryreservoir connected to the reservoir, by one or more flow paths wherein(i) the reservoir is adapted to accommodate a reduction in volume, thevolume reduction pressurizing the fluid constituent and thereby creatingthe fluid flow path into the reaction chamber, (ii) the temperaturecontrol means comprises a plug associated with the or each flow path,which is adapted to open when the ambient temperature of thesurroundings reaches a pre-defined temperature, and (iii) the or eachplug is made from a material, which melts in response to an increase inthe ambient temperature of the container.
 10. The self heating containerof claim 9, wherein each plug melts at a different temperature.